1. Field of the Invention
The invention relates generally to retractable devices which have an operating element movable between an exposed, working position and a covered, storage position More particularly, the invention relates to retractable, surgical devices which have an operating element lockable in a plurality of selected cutting positions. Still more particularly, the invention relates to disposable, retractable surgical cutting devices.
2. Description of the Prior Art
Retractable cutting devices for use in surgical procedures are commonly known in the prior art. The retractable nature of such devices assures that the cutting surface will be held retracted within the device in such a way as to not interfere with the placement of the device adjacent the area to be operated upon, whereupon the cutting surface may be extended in order to perform the desired surgical procedure without injuring surrounding tissue.
The present invention is particularly adaptable to small cutting instruments and is, therefore, intended primarily for use in arthroscopy or microsurgery of the knee and other joints in humans (or other animals). It will be understood, however, that the principles of this invention are equally applicable to other surgical, and even non-surgical cutting and non-cutting devices For these reasons, the use herein of the terms "knife", "cutting", "blades" and the like should not be considered as limiting the scope of the invention.
Arthroscopy involves the use of viewing, probing and cutting devices that can be utilized through a very small opening in the patient's skin. The procedure necessarily involves the steps of insertion, retraction and manipulation of various devices through the skin to an area to be operated upon. Such steps are primarily blind until the device comes into view of the arthroscope. Consequently, it is desirable that any cutting or other potentially dangerous instruments be protected from either unintentionally injuring the patient or from being damaged by other tools during the blind maneuvers. Retractable cutting devices are obviously quite desirable in arthroscopic procedures.
Prior art arthroscopic cutting devices are generally available in either one of two configurations: (1) a separate sheath configuration having an unsheathed and unprotected disposable operating member (e.g. knife blade) situated on long, reusable handles and intended to be inserted within tubular sheaths previously placed separately through the skin, or (2) a combination configuration having a disposable sheathed blade which is retractable within a sheath on a permanent handle, the sheath being inserted through the skin simultaneously with the knife. The separate sheath system is cumbersome to use and almost always has a dulling effect on the cutting surfaces of the operating member as they rub the inner wall of the sheath. The combination configuration is a safer system, although it still has several undesirable characteristics. The permanent handle is very costly, and, therefore, usually only one handle is available. This requires the surgeon to decide which operating member or cutting blade (out of possibly 20 or so typical configurations) should be placed in the handle before surgery. Alternatively, the surgeon must wait until the surgical procedure has begun in order to decide which blade to use, whereupon the blade must be removed from its sterile packaging and assembled into the handle. This procedure obviously affects the surgeon's efficiency and concentration. Additionally, the procedure inhibits the surgeon from using a variety of blades which may otherwise be the most optimal configuration for u se during various portions of the procedure. Once the sterile package is opened and a blade is inserted into the handle, the surgeon will tend to complete the procedure using this first blade rather than waiting to have a (possibly more appropriate) blade or other device inserted into the handle.
The prior art disposable blade/permanent handle system incorporates a locking method to lock the knife blade relative to the handle in an extended position during surgery. Prior art locking mechanisms are cumbersome and require more than one motion to affect any movement of the blade relative to its housing. One type of locking device, shown for example in U.S. Pat. No. 4,674,500 (DeSatnick), requires the surgeon to push a slide mechanism longitudinally forward and rotate it laterally relative to the handle in order to lock the slide mechanism into a detent Such a mechanism is awkward to use and has been found to be susceptible to accidental unlocking. The design also necessarily introduces "play" or uncontrolled movement in the blades, which movement must be dampened by deliberately bending the blades (or their support shafts) to cause a binding interference fit within the sheath attached to the handle. This results in a very rough actuation and retraction of the blade. Another type of prior art locking device, shown for example in U.S. Pat. No. 4,491,132 (Aikens), requires the surgeon to transversely deflect a locking pin to enable a blade to be slid longitudinally to place the locking pin into engagement with a selected detent in the handle. This mechanism is also difficult to use.
Additionally, the prior art disposable blade/permanent handle devices may tempt people to reuse already used blades. Even though the blades may have been sterilized prior to reuse, this is a risky procedure, not only because the blades may not be sterilized well enough, but because the blades may not be sharp enough for subsequent uses, thereby affecting the surgical procedure to be performed on subsequent patients.
In order to overcome the foregoing disadvantages, it is an object of this invention to provide a retractable surgical instrument which is disposable.
It is a further object of this invention to provide a retractable surgical instrument having a handle and an operating or cutting element, the entire device including the handle assembly being disposable.
It is an additional object of this invention to produce a high quality retractable arthroscopic knife which is relatively inexpensive and disposable.
It is still another object of this invention to provide a retractable, sheathed surgical instrument having an improved locking mechanism enabling the active, operating element of the instrument to be locked into a plurality of extended positions relative to a housing or sheath.
It is still another object of this invention t provide a retractable instrument having a locking mechanism which is automatically actuated by a single manual motion of the user and which is not easily disengaged during use. It is a further object to disclose a method for achieving these purposes in a retractable surgical instrument.
It is an additional object of this invention to provide a retractable surgical instrument wherein the actual operating element or cutting surface, a covering sheath and the instrument handle are integrally formed in one nondisassemblable unit.